Isolated tubercular hypoglossal nerve paralysis

Introduction

Hypoglossal paralysis is common in malignancy involving the skull base or parapharyngeal space and is usually associated with other higher cranial nerves (vagus and accessory spinal nerve) paralysis. Isolated hypoglossal paralysis is rare; it can, however, manifest in trauma, submandibular cancer, nodal metastasis and meningitis.

Nasopharyngeal tuberculosis (TB) is a rare disorder and can present with lymphadenopathy, nasal obstruction, epistaxis and discharge. Cranial nerve paralysis can occur with associated adenopathy or tubercular meningitis. We present a case of unilateral hypoglossal paralysis in a patient with nasopharyngeal TB and review its pathogenesis.

Case report

A 31-year-old woman presented with a persistent dull headache for 1 month. Within 2 weeks of this illness, she had insidious and progressive difficulty in swallowing and speaking. There was no other relevant history. Examination revealed the tongue to be deviated towards the right (Figure 1). Oropharyngeal, laryngeal, ear and neck examination was unremarkable. The possibility of a skull base tumour was mooted. Nasal endoscopic examination revealed an irregular firm tumour arising from the roof of nasopharynx (Figure 2). This finding favoured nasopharyngeal malignancy and so a punch biopsy was taken. Radiological scans demonstrated a tumour arising from the posterior wall of nasopharynx measuring approximately 1.4 × 1.9 cm with craniocaudal extension of 2 cm (Figure 3). There was no bony erosion or intracranial extension. The cerebrum, cranial nerves and neck were noted as grossly normal. Laboratory investigations and chest radiograph were unremarkable. Histopathological examination confirmed granulomata with caseation, and giant and Langerhans cells indicating tuberculosis (TB) (Figure 4). Nonetheless, Ziehl-Neelsen staining and solid culture were negative. OPEN IN VIEWER

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Figure 2.

Nasal endoscopic view showing tumour in the nasopharynx.

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Figure 3.

(a) CT scan showing homogenous tumour in the nasopharynx; (b) MRI showing tumour in nasopharynx with normal brain and neck.

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Figure 4.

Microphotograph showing granulomas with caseation, giant and Langerhans cells (H&E, 40×).

Systemic examination revealed no other tubercular focus and the patient was treated with anti-tubercular medication. Hypoglossal nerve function recovered within 1 month. Follow-up nasal endoscopy in the fifth month of treatment showed that the nasopharyngeal tumour had regressed with minimal muscular atrophy (Figures 5 and 6). OPEN IN VIEWER

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Figure 6.

Follow-up clinical photograph showing minimal muscular atrophy and palsy.

Discussion

Hypoglossal nerve involvement is commonly associated with other cranial nerve palsies and isolated hypoglossal nerve paralysis is rare.^1,2 The latter is often an ominous prognostic sign. Commonly, unilateral hypoglossal nerve paralysis occurs in nasopharyngeal carcinomas, skull base metastasis, Guillain Barre syndrome, trauma, meningitis, Epstein Barr virus infection, HIV and rarely dissection of the internal carotid artery.^1–3 Idiopathic cranial nerve paralysis may be transient, diagnosed by exclusion and usually recovers without sequel.^4–6

Although the pathogenesis of hypoglossal paralysis in our case remains unclear, it could have been caused by minimal invasion of the nerve or meningeal membranes. A single case of craniocervical TB with unilateral hypoglossal palsy and four cases of tubercular meningitis with unilateral hypoglossal paralysis have been documented in the literature.^1,7

TB is endemic in the Indian subcontinent but it is rare in the nose and paranasal sinus. ⁸ It commonly presents with cervical lymphadenopathy, nasal obstruction, rhinorrhoea, epistaxis, otalgia and hearing loss whereas 12–30% present with constitutional symptoms.^9,10 The pathogenesis of nasopharyngeal TB remains unclear with three possible mechanisms: (1) direct infection; (2) activation of dormant mycobacteria in adenoid’ and (3) spread from pulmonary TB.^11,12 Clinically, it may manifest as diffuse inflammation and ulceration, or polypoidal tumour formation, although the mucosa may remain normal. ¹³

A limitation in terms of diagnosis in our case is that we were unable to correlate hypoglossal paralysis definitively with nasopharyngeal TB. Despite showing recovery with anti-tubercular treatment, this case could still have been a transient hypoglossal palsy. Furthermore, tubercular staining in histopathology may not be 100% reliable and TB culture has its own limitations. A causative relationship between TB and hypoglossal nerve palsy therefore needs to be drawn cautiously.